Structural studies of wear debris from carbon-carbon composite aircraft brakes

Microstructural studies using X-ray diffraction, SEM, and optical microscop y were made of wear debris from carbon-carbon composite aircraft brakes pro duced under different simulated braking operations. Under simulated cold ta xiing conditions, particulate wear debris comprising a disordered carbon ph ase containing fibre fragments is formed. The disordered phase is produced mainly by shear deformation of the graphitic CVI matrix in the parent carbo n-carbon composite. Under simulated landing conditions the wear debris is p artly transformed by shear processes into a friction film with a similar di sordered microstructure to the wear debris formed during taxiing. The frict ion film is formed as a result of the higher power density and interfacial temperatures during landing. The very high power densities and interface te mperatures that apply during rejected take-off result in shear-stress assis ted graphitisation of the friction film, but with a fine mosaic texture tha t is quite different from the texture of the CVI matrix in the parent compo site. (C) 1999 Elsevier Science Ltd. All rights reserved.